The present invention claims the benefit of Korean Patent Application No. 2004-0086470 filed in Korea on Oct. 28, 2004, which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an apparatus for a display device, and more particularly, to an apparatus having a gas injector.
2. Discussion of the Related Art
Flat panel display (FPD) devices having portability and low power consumption have been a subject of increasing research in the present information age. Among the various types of FPD devices, liquid crystal display (LCD) devices are commonly used in notebook and desktop computers because of their high resolution, capability of displaying colored images, and high quality image display. However, LCD devices are not an emissive type but a non-emissive type. Accordingly, LCD devices have limitations in brightness, contrast ratio, viewing angle and size enlargement.
To overcome the limitations of LCD devices, organic electroluminescent display (OELD) devices have been researched. Since OELD devices are an emissive type, viewing angel and contrast ratio are improved in contrast with LCD devices. In addition, since a backlight unit is not required, OELD devices have portability and low power consumption. Specifically, OELD devices can be manufactured at a low cost and a simple process; particularly since a manufacturing process of OELD devices is very simple in contrast with LCD devices or plasma display panel (PDP) devices, only deposition and encapsulation apparatuses are necessary for manufacturing OELD devices.
FIG. 1 is a schematic cross-sectional view showing an organic electroluminescent display device according to the related art. In FIG. 1, an organic electroluminescent display device 10 includes an anode 11, a cathode 15, and an emission layer 13 between the anode 11 and the cathode 15. A hole transporting layer 12 is formed between the anode 11 and the emission layer 13, and an electron transporting layer 14 is formed between the cathode 15 and the emission layer 13. The hole transporting layer 12, the emission layer 13 and the electron transporting layer 14 may be formed of an organic material. In addition, the anode 11 may be formed of indium-tin-oxide (ITO) and the cathode 15 may be formed of aluminum (Al).
When voltages are applied to the anode 11 and the cathode 15, holes are injected from the anode 11 into the emission layer 13 through the hole transporting layer 12 and electrons are injected from the cathode 15 into the emission layer 13 through the electron transporting layer 14. The holes and the electrons are recombined in the emission layer 13 to generate excitons. The excitons are transitioned from an excited state to a ground state so that light can be irradiated from the emission layer 13 for displaying images. The emission layer may include organic materials that emit red, green and blue colors of light in each pixel region. For example, the organic materials may be selected from one of Alq3, CuPc, TDP and NPB. In addition, dopants are added into the organic materials to display different colors. For example, DCJTB may be added for red color. Similarly, coumarine derivatives or quinacridone derivatives may be added for green color, and DPA may be added for blue color.
A layer including organic materials may be formed using evaporation. Accordingly, source organic materials in a solid state are evaporated and the evaporated source organic materials are deposited on a substrate. A shadow mask having a pattern may be disposed over the substrate and the substrate may be partially exposed through the shadow mask.
FIGS. 2A to 2C are schematic cross-sectional views showing evaporation apparatuses for forming an organic material thin film according to the related art. In FIG. 2A, a susceptor 22 and a point evaporation source 24a are disposed at an upper portion and a lower portion in a chamber 21 of an evaporation apparatus 20, respectively. A substrate “S” is adhered to a bottom surface of the susceptor 22 and a shadow mask 23 having open patterns is disposed between the substrate and the point evaporation source 24a. The shadow mask 23 may be disposed adjacent to the substrate “S.” Source organic materials are evaporated in the point evaporation source 24 and the evaporated source organic materials is deposited onto the substrate “S” through the open patterns of the shadow mask 23. For example, a ceramic crucible heated by a hot wire may be used as the point evaporation source 24a. To improve uniformity of a thin film formed on the substrate “S,” the substrate “S” is disposed far from the point evaporation source 24a so that the evaporated organic materials can be sufficiently diffused. In addition, the susceptor 22 having the substrate “S” may be rotated about a rotation axis 25.
In FIG. 2B, a susceptor 22 and a line evaporation source 24b are disposed at an upper portion and a lower portion in a chamber 21 of an evaporation apparatus 20, respectively. The line evaporation source 24b horizontally moves along a transfer line 26 and has a bar shape perpendicular to the transfer line 26. A substrate “S” is adhered to a bottom surface of the susceptor 22 and a shadow mask 23 having open patterns is disposed between the substrate and the line evaporation source 24b. Since the line evaporation source 24b moves, the substrate “S” may not rotate. The shadow mask 23 may be disposed adjacent to the substrate “S.” Source organic materials are evaporated in the line evaporation source 24b and the evaporated source organic materials is deposited onto the substrate “S” through the open patterns of the shadow mask 23.
In FIG. 2C, a susceptor 22 and a line injector 27 are disposed at a lower portion and an upper portion in a chamber 21 of an evaporation apparatus 20, respectively. Organic materials are evaporated in an external evaporation source 30 outside the chamber 21 and are supplied to the line injector 27. Carrier gases are supplied to the external evaporation source 30 through a carrier gas inlet 33 to carry the evaporated organic materials. Accordingly, the evaporated organic materials and the carrier gases mixed in the external evaporation source 30 are supplied to the line injector 27 through a source gas inlet 32. A substrate “S” is disposed on a susceptor 22, and a shadow mask 23 having open patterns is disposed between the line injector 27 and the substrate “S.” In addition, the line injector 27 horizontally moves along a transfer line 28 and has a bar shape perpendicular to the transfer line 28.
Accordingly, the line injector 27 in the chamber 21 sprays the organic materials evaporated outside the chamber 21 onto the substrate “S” through the open patterns of the shadow mask 23. When the line injector 27 moves along the transfer line 28, the external evaporation source 30 connected to the line injector 27 through the source gas inlet 32 moves along an external transfer line 31. A bellows is formed in a border region between the chamber 21 and the source gas inlet 32 for airtightness.
However, there are several drawbacks in evaporation apparatuses according to the related art. To obtain superior uniformity of a thin film in an evaporation apparatus of FIG. 2A, the chamber 21 should be kept in a high vacuum condition to increase evaporation pressure of the organic materials. In addition, a distance between the substrate “S” and the point evaporation source 24a should be maximized. Accordingly, efficiency of the organic materials is very low, and uniformity of a thin film is reduced as the substrate size increases. Moreover, since the shadow mask 23 is disposed under the substrate “S,” the shadow mask 23 may be warped. In addition, as the substrate “S” increases in size, the line evaporation source 24b of an evaporation apparatus of FIG. 2B is elongated. As a result, amount of the organic materials also increases. In addition, since a distance between the substrate “S” and the line evaporation source 24b should be maximized for superior uniformity, efficiency of the organic materials is reduced. Further, since the shadow mask 23 is disposed under the substrate “S,” the shadow mask 23 may be warped as in FIG. 2A. In an evaporation apparatus of FIG. 2C, warpage of the shadow mask 23 is prevented because the shadow mask 23 is disposed on the substrate “S.” However, as the substrate size increases, the source gas inlet 32 through which the evaporated organic materials are supplied to the line injector 27 is elongated. In addition, since the external evaporation source 30 moves corresponding to the line injector 27, a footprint of the evaporation apparatus increases. Further, since the source gas inlet should be kept in a high temperature condition, for example, 100° C. to 500° C., to prevent re-condensation of the evaporated organic materials during a transfer, the evaporation apparatus becomes complicated. The above drawbacks are not limited to an evaporation apparatus using organic materials but may occur in an apparatus evaporating source materials for display devices.